Earth's Geology: Processes, Layers, and Plate Tectonics

What does physical geology study?

Earth's materials and the processes that affect them.

What does historical geology study?

Earth's origin and how Earth has changed through time.

What is uniformitarianism?

The idea that the same natural processes operating today also operated in Earth's past.

About how old is Earth?

About 4.6 billion years.

What are Earth's four major spheres?

Geosphere, hydrosphere, atmosphere, and biosphere.

Why is Earth considered a system?

Its different spheres interact with and affect one another.

What is a scientific hypothesis?

A testable explanation.

What is a scientific theory?

A well-supported explanation backed by extensive evidence.

Does a scientific theory eventually become a scientific law?

No. Theories explain phenomena while laws describe consistent relationships.

What are Earth's three compositional layers?

Crust, mantle, and core.

What are Earth's five physical/mechanical layers?

Lithosphere, asthenosphere, mesosphere, outer core, and inner core.

Which physical layer of Earth is rigid?

Lithosphere.

Which layer is weak/plastic and allows tectonic plates to move?

Asthenosphere.

Which part of Earth's core is liquid?

Outer core.

Which part of Earth's core is solid?

Inner core.

What process turns magma or lava into igneous rock?

Cooling and crystallization.

Where does intrusive igneous rock form?

Below Earth's surface.

Where does extrusive igneous rock form?

At Earth's surface.

What turns sediment into sedimentary rock?

Compaction and cementation.

What turns existing rock into metamorphic rock?

Heat and pressure.

What turns rock into magma?

Melting.

What processes produce sediment from existing rocks?

Weathering and erosion.

What two ideas are combined in the theory of plate tectonics?

Continental drift and seafloor spreading.

Who proposed continental drift?

Alfred Wegener.

What was Pangaea?

A supercontinent containing most of Earth's continental land.

What evidence supports continental drift?

Matching fossils, rocks and mountain belts, continental shapes, and evidence of ancient climates.

What is seafloor spreading?

New oceanic crust forms at mid-ocean ridges and moves outward.

Where is the youngest oceanic crust found?

Closest to a mid-ocean ridge.

What are the three main types of plate boundaries?

Divergent, convergent, and transform.

What happens at a divergent boundary?

Plates move apart.

What happens at a convergent boundary?

Plates move toward each other.

What happens at a transform boundary?

Plates slide past each other.

What major feature forms at an oceanic divergent boundary?

A mid-ocean ridge.

What happens at a subduction zone?

One tectonic plate sinks beneath another.

At an oceanic-continental convergent boundary, which plate subducts?

The oceanic plate.

What features commonly form at an oceanic-continental convergent boundary?

A trench and a continental volcanic arc.

What features commonly form at an oceanic-oceanic convergent boundary?

A trench and a volcanic island arc.

What commonly forms at a continental-continental convergent boundary?

Large mountain ranges.

Why doesn't continental crust usually subduct easily?

It is relatively buoyant.

What process within the mantle helps drive plate movement?

Convection.

A diagram shows a trench and volcanic islands where two oceanic plates meet. What boundary is this?

Oceanic-oceanic convergent boundary.

A diagram shows a mid-ocean ridge with plates moving apart. What boundary is this?

Divergent boundary.

A diagram shows an oceanic plate subducting beneath a continent with volcanoes on land. What boundary is this?

Oceanic-continental convergent boundary.

What is a mineral?

A naturally occurring, inorganic solid with an orderly crystalline structure and a definite chemical composition.

Can a human-made substance be considered a mineral?

No.

Are minerals generally inorganic?

Yes.

What is mineral hardness?

Resistance to scratching.

What scale measures mineral hardness?

Mohs hardness scale.

What is the softest mineral on the Mohs scale?

Talc, with a hardness of 1.

What is the hardest mineral on the Mohs scale?

Diamond, with a hardness of 10.

What is streak?

The color of a mineral in powdered form.

Why can streak be more useful than a mineral's surface color?

Surface color can vary while streak is often more consistent.

What is luster?

How light reflects from a mineral's surface.

What are the two broad categories of mineral luster?

Metallic and nonmetallic.

What is cleavage?

A mineral's tendency to break along smooth, flat planes.

What is fracture?

A mineral breaking irregularly instead of along cleavage planes.

What is specific gravity?

A comparison of a mineral's density to the density of water.

What is the most abundant mineral group?

Silicates.

Which two elements are fundamental to silicate minerals?

Silicon and oxygen.

What is an ore?

A material containing something valuable that can be extracted economically.

What is a gemstone?

A mineral valued primarily for its beauty, rarity, and durability.

Why did early Earth develop a layered structure?

Differences in density caused materials to separate during differentiation.

During Earth's differentiation, what happened to denser materials?

They sank toward Earth's center.

During Earth's differentiation, what happened to less-dense materials?

They rose toward Earth's surface.

What are P-waves?

Fast compressional seismic waves.

What materials can P-waves travel through?

Solids and liquids.

What are S-waves?

Shear seismic waves.

What materials can S-waves travel through?

Solids only.

Why can't S-waves travel through Earth's outer core?

The outer core is liquid.

Which seismic waves travel faster, P-waves or S-waves?

P-waves.

What seismic evidence helped scientists determine that Earth's outer core is liquid?

S-waves do not pass through it and P-waves refract as they travel through it.

What is a seismic shadow zone?

An area where particular seismic waves from an earthquake are not detected.

What can happen when seismic waves encounter a boundary between materials with different properties?

They can reflect and refract.

What is seismic refraction?

The bending of a seismic wave as its velocity changes between materials.

What is seismic reflection?

A seismic wave bouncing back from a boundary.

What is seismic tomography?

Using seismic-wave data to create images of Earth's interior.

What are the three methods of heat transfer?

Conduction, convection, and radiation.

What is conduction?

Heat transfer through direct molecular contact.

What is convection?

Heat transfer through the movement or circulation of material.

What is radiation?

Heat transfer through electromagnetic waves.

What are some characteristics that make Earth habitable?

Liquid water, suitable temperatures, an atmosphere, energy, and necessary chemical elements.

Which happened first, the Big Bang or the formation of Earth?

The Big Bang.

Approximately how old is the universe?

About 13.8 billion years.

Approximately how old is Earth?

About 4.6 billion years.

Where did much of Earth's early atmosphere come from?

Volcanic outgassing.

How did Earth's oceans develop?

Earth cooled, water vapor condensed, and liquid water accumulated.

What eventually added large amounts of oxygen to Earth's atmosphere?

Photosynthetic organisms.

What is the supercontinent cycle?

Continents repeatedly assemble into supercontinents and later break apart.

What major supercontinent existed before Pangaea?

Rodinia.

Pangaea assembled primarily during which geologic era?

Paleozoic.

Pangaea began breaking apart during which geologic era?

Mesozoic.

What does Paleozoic mean?

Ancient life.

What does Mesozoic mean?

Middle life.

What does Cenozoic mean?

Recent life.

What is the correct order of the three major geologic eras from oldest to youngest?

Paleozoic, Mesozoic, Cenozoic.

Which era is especially associated with dinosaurs?

Mesozoic.

Which era is associated with extensive diversification of mammals?

Cenozoic.

What major event occurred at the end of the Paleozoic?

The Permian mass extinction.

What major event occurred at the end of the Mesozoic?

The K-Pg mass extinction, which included the extinction of non-avian dinosaurs.